1. Field of the Invention
The present invention relates in general to the field of integrated circuit design, and more particularly to a system and method for integrated circuit module tamperproof mode personalization.
2. Description of the Related Art
Integrated circuits are typically manufactured by fabricating a number of “chips” on a wafer of semiconductor material, such as silicon, and then packaging the individual integrated circuit chips in modules. The modules typically provide wiring to connect circuits within the integrated circuit and external wiring, such as pins or a grid array that fit into a socket of a printed circuit board.
Integrated circuits perform processing and other functions with transistors etched into a semiconductor substrate and interconnected by wiring. Over time fabrication techniques have improved to build integrated circuits with greater numbers of transistors on a substrate of a given size. This has allowed integration levels that enable unprecedented performance and feature content in even the smallest physical system building blocks. For example, an integrated circuit having relatively small footprints can include encryption features that enhance the security of the system that uses the integrated circuit.
Much of the expense of manufacture of an integrated circuit is in the design of the integrated circuit. Often, a common integrated circuit design is sold to different market segments by selectively enabling and disabling features on the integrated circuit. For example, the integrated circuit has features selectively disabled by blowing “fuses” within the integrated circuit as part of the manufacture process. Including fuses reduces design expense by allowing a common design to have different features enabled. For instance, fuses built into an integrated circuit can selectively disable encryption features in order to comply with export control laws that restrict the sale of integrated circuits with encryption technology. Essentially, the integrated circuit is personalized at manufacture to include only selected features.
Typically fuses are blown at final wafer test although access can be included in modules so that fuses are blown during module test. One difficulty with blowing fuses at module test is that end users may also have access to a fuse blow port of the module so that accidental or malicious reconfiguration of the data blown into a fuse array of the integrated circuit might result in enablement of features meant to be disabled. However, having a module port for blowing fuses at module test or even post-module test provides greater flexibility in the manufacture and distribution of integrated circuit products.